Bakery products, pastries and confectionery are often extruded by forcing a substance placed under pressure through a nozzle arrangement to form a strand. The strand may as such be carried away by a conveyor belt or it may be divided into short portions. The external shape, in particular the peripheral shape of the strand is dependent upon the nozzle arrangement.
From the document U.S. Pat. No. 5,637,341, which forms the basis for the preamble of claim 1, a device for manufacturing plaited dough products is known, which comprises three driving wheels, which are arranged in a row and with which four nozzle plates are associated. The nozzle plates are alternately turned over between the driving wheels and, in the process, plait the emerging dough strands. A nozzle plate, while it is moved by a driving wheel, is rotated about its axis. With such a device it is not possible to produce filled dough products.
From EP-A-0 704 158 a nozzle arrangement is known, in which a stationary inner nozzle is surrounded by a middle and an outer nozzle, which are formed in a rotor. All of the nozzles are disposed coaxially. With such a nozzle arrangement it is possible to manufacture dough products having one strand, which comprises a filling and two enveloping doughy substances.
From EP-A-0 168 255 and EP-A-0 177 175 devices for co-extruding two substances are known, which extrude an inner substance through a nozzle and an outer substance containing granular particles through a hopper surrounding the nozzle, wherein the substances are combined to form a strand. The hopper at its mouth has sharp edges so that the granular particles in the outer substance may pass onto the surface. The mouth of the hopper may be of a toothed design so that the particles also project from the surface. The composite strand is carried away by a conveyor belt. By said means it is possible to produce from two substances a bakery product, which has a rectilinear elongate shape and has granular particles at the surface.
From EP-A-0 202 143 A2 a triple extruder is known, by means of which an inner substance may be coated with a first outer substance, and the latter may be coated with a second outer substance. The inner substance is fed through a middle feed channel to an inner nozzle. An outer nozzle surrounds the inner nozzle and is supplied with the outer substance through a lateral feed channel. A hopper surrounds the outer nozzle. The second outer substance is supplied through the hopper. The outer nozzle and the hopper each form an annular space around the inner nozzle. In longitudinal section, said annular spaces have an angular shape. With such a triple extruder it is possible to produce a likewise elongate, externally rectilinear bakery product.
U.S. Pat. No. 5,120,554 describes a stand-alone nozzle head for extruding a doughy substance. The nozzle head at its periphery has a plurality of nozzle arrangements. The nozzle arrangements are formed in each case by a double nozzle for manufacturing filled bakery products. Said double nozzles each have an inner nozzle, which is supplied through an individual feed channel, and an outer nozzle. The outer nozzles are supplied via a common cylindrical feed chamber through lateral channels. The nozzle head enables simultaneous extrusion of a plurality of filled, straight strands.
From U.S. Pat. No. 5,518,749 and WO 97/25881 a method and a device for manufacturing twisted cereal products are known. A rotor, which extends through a chamber and runs into an opening of the chamber, forms an inner nozzle, through which ah inner substance is feedable. A second substance is feedable through a lateral channel into the chamber. Between the opening of the chamber and the rotor there is an annular gap, through which the second substance may exit. The annular gap corresponds to an outer nozzle. When the rotor, and/or the inner nozzle, rotates, a product having a twisted outer substance layer and a filling is produced. In said case, however, the twisting of the outer substance layer is highly dependent upon the properties of the outer substance, such as e.g. its flow behaviour and viscosity. The extruded cereal products therefore do not always have a sufficiently uniform shape.